Fairness and being treated with respect in the workplace?

I have an old knee injury that flares up every now and then, and as a waitress, it happens alot. I recently called into work saying I could not work, and I got treated very rudely. I came in with a doctors not, and I got more rudeness. I went in today to get next weeks schedule, and to find out if there was anyway I could not work tomorrow as scheduled, and once again I got treated unfairly. All this rudeness is from one manager, and she's just the istant manager. What actions should I take? Should I quit and get on welfare (HAHA)? Just call in tomorrow? Call corprate or talk to another manager?